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Impaired parkin-mediated mitochondrial targeting to autophagosomes differentially contributes to tissue pathology in lysosomal storage diseases.

de Pablo-Latorre R, Saide A, Polishhuck EV, Nusco E, Fraldi A, Ballabio A - Hum. Mol. Genet. (2012)

Bottom Line: In LSDs, autophagic stress has been associated to mitochondrial accumulation and dysfunction.We demonstrated that in MSD liver reduced parkin levels resulted in inefficient mitochondrial priming, thus contributing to the accumulation of giant mitochondria that are located outside autophagic vesicles ultimately leading to cytochrome c release and apoptotic cell death.Morphological and functional changes were also observed in mitochondria from MSD brain but these were not directly associated with neuronal cell loss, suggesting a secondary contribution of mitochondria to neurodegeneration.

View Article: PubMed Central - PubMed

Affiliation: Telethon Institute of Genetics and Medicine, Naples 80131, Italy.

ABSTRACT
Dysfunctional mitochondria are a well-known disease hallmark. The accumulation of aberrant mitochondria can alter cell homeostasis, thus resulting in tissue degeneration. Lysosomal storage disorders (LSDs) are a group of inherited diseases characterized by the buildup of undegraded material inside the lysosomes that leads to autophagic-lysosomal dysfunction. In LSDs, autophagic stress has been associated to mitochondrial accumulation and dysfunction. However, the mechanisms underlying mitochondrial aberrations and how these are involved in tissue pathogenesis remain largely unexplored. In normal conditions, mitochondrial clearance occurs by mitophagy, a selective form of autophagy, which relies on a parkin-mediated mitochondrial priming and subsequent sequestration by autophagosomes. Here, we performed a detailed analysis of key steps of mitophagy in a mouse model of multiple sulfatase deficiency (MSD), a severe type of LSD characterized by both neurological and systemic involvement. We demonstrated that in MSD liver reduced parkin levels resulted in inefficient mitochondrial priming, thus contributing to the accumulation of giant mitochondria that are located outside autophagic vesicles ultimately leading to cytochrome c release and apoptotic cell death. Morphological and functional changes were also observed in mitochondria from MSD brain but these were not directly associated with neuronal cell loss, suggesting a secondary contribution of mitochondria to neurodegeneration. Together, these data shed new light on the mechanisms underlying mitochondrial dysfunction in LSDs and on their tissue-specific differential contribution to the pathogenesis of this group of metabolic disorders.

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Autophagy is inhibited at advanced stages of MSD liver pathology. (A) LC3 immunoblots on total liver homogenates from MSD (n= 3) and control mice (n= 3) at P15, 1 month and 3 months. Autophagosome accumulation is expressed as the fold change of the LC3-II/actin ratio compared with control; **P < 0.01, ***P < 0.005. (B) Levels of BECN-1 were measured in liver extracts from MSD (n= 3) and control mice (n= 3) at P15, 1 month and 3 months. The BECN-1/actin ratio is expressed as fold changes; **P < 0.01. (C) Becn1 mRNA levels were determined by real-time PCR in liver samples (n= 3) at 3 months.
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DDR610F6: Autophagy is inhibited at advanced stages of MSD liver pathology. (A) LC3 immunoblots on total liver homogenates from MSD (n= 3) and control mice (n= 3) at P15, 1 month and 3 months. Autophagosome accumulation is expressed as the fold change of the LC3-II/actin ratio compared with control; **P < 0.01, ***P < 0.005. (B) Levels of BECN-1 were measured in liver extracts from MSD (n= 3) and control mice (n= 3) at P15, 1 month and 3 months. The BECN-1/actin ratio is expressed as fold changes; **P < 0.01. (C) Becn1 mRNA levels were determined by real-time PCR in liver samples (n= 3) at 3 months.

Mentions: We monitored the levels of LC3-II in MSD liver at different time points and found that the LC3-II/actin ratio was significantly increased compared with control (Fig. 6A). These data are consistent with the impairment of autophagosome maturation already reported in MSD (30,35). Interestingly, LC3-II accumulation was not associated with the induction of beclin-1 (BECN-1) at this stage of pathology. On the contrary, beclin-1 protein levels were reduced, whereas its mRNA levels remained unaltered (Fig. 6B and C).Figure 6.


Impaired parkin-mediated mitochondrial targeting to autophagosomes differentially contributes to tissue pathology in lysosomal storage diseases.

de Pablo-Latorre R, Saide A, Polishhuck EV, Nusco E, Fraldi A, Ballabio A - Hum. Mol. Genet. (2012)

Autophagy is inhibited at advanced stages of MSD liver pathology. (A) LC3 immunoblots on total liver homogenates from MSD (n= 3) and control mice (n= 3) at P15, 1 month and 3 months. Autophagosome accumulation is expressed as the fold change of the LC3-II/actin ratio compared with control; **P < 0.01, ***P < 0.005. (B) Levels of BECN-1 were measured in liver extracts from MSD (n= 3) and control mice (n= 3) at P15, 1 month and 3 months. The BECN-1/actin ratio is expressed as fold changes; **P < 0.01. (C) Becn1 mRNA levels were determined by real-time PCR in liver samples (n= 3) at 3 months.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3313794&req=5

DDR610F6: Autophagy is inhibited at advanced stages of MSD liver pathology. (A) LC3 immunoblots on total liver homogenates from MSD (n= 3) and control mice (n= 3) at P15, 1 month and 3 months. Autophagosome accumulation is expressed as the fold change of the LC3-II/actin ratio compared with control; **P < 0.01, ***P < 0.005. (B) Levels of BECN-1 were measured in liver extracts from MSD (n= 3) and control mice (n= 3) at P15, 1 month and 3 months. The BECN-1/actin ratio is expressed as fold changes; **P < 0.01. (C) Becn1 mRNA levels were determined by real-time PCR in liver samples (n= 3) at 3 months.
Mentions: We monitored the levels of LC3-II in MSD liver at different time points and found that the LC3-II/actin ratio was significantly increased compared with control (Fig. 6A). These data are consistent with the impairment of autophagosome maturation already reported in MSD (30,35). Interestingly, LC3-II accumulation was not associated with the induction of beclin-1 (BECN-1) at this stage of pathology. On the contrary, beclin-1 protein levels were reduced, whereas its mRNA levels remained unaltered (Fig. 6B and C).Figure 6.

Bottom Line: In LSDs, autophagic stress has been associated to mitochondrial accumulation and dysfunction.We demonstrated that in MSD liver reduced parkin levels resulted in inefficient mitochondrial priming, thus contributing to the accumulation of giant mitochondria that are located outside autophagic vesicles ultimately leading to cytochrome c release and apoptotic cell death.Morphological and functional changes were also observed in mitochondria from MSD brain but these were not directly associated with neuronal cell loss, suggesting a secondary contribution of mitochondria to neurodegeneration.

View Article: PubMed Central - PubMed

Affiliation: Telethon Institute of Genetics and Medicine, Naples 80131, Italy.

ABSTRACT
Dysfunctional mitochondria are a well-known disease hallmark. The accumulation of aberrant mitochondria can alter cell homeostasis, thus resulting in tissue degeneration. Lysosomal storage disorders (LSDs) are a group of inherited diseases characterized by the buildup of undegraded material inside the lysosomes that leads to autophagic-lysosomal dysfunction. In LSDs, autophagic stress has been associated to mitochondrial accumulation and dysfunction. However, the mechanisms underlying mitochondrial aberrations and how these are involved in tissue pathogenesis remain largely unexplored. In normal conditions, mitochondrial clearance occurs by mitophagy, a selective form of autophagy, which relies on a parkin-mediated mitochondrial priming and subsequent sequestration by autophagosomes. Here, we performed a detailed analysis of key steps of mitophagy in a mouse model of multiple sulfatase deficiency (MSD), a severe type of LSD characterized by both neurological and systemic involvement. We demonstrated that in MSD liver reduced parkin levels resulted in inefficient mitochondrial priming, thus contributing to the accumulation of giant mitochondria that are located outside autophagic vesicles ultimately leading to cytochrome c release and apoptotic cell death. Morphological and functional changes were also observed in mitochondria from MSD brain but these were not directly associated with neuronal cell loss, suggesting a secondary contribution of mitochondria to neurodegeneration. Together, these data shed new light on the mechanisms underlying mitochondrial dysfunction in LSDs and on their tissue-specific differential contribution to the pathogenesis of this group of metabolic disorders.

Show MeSH
Related in: MedlinePlus